From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set, a user fault may trigger show_pte() without any lock. If another thread in the same process concurrently calls munmap(), the page table pages may be freed while show_pte() is still traversing them, causing a use-after-free in show_pte(). If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table of PMD are freed when show_pte() is running. Acquire mmap_write_lock() around show_pte() for user faults to fix the contention. For user faults, additionally restrict that show_pte() is called only when the addr is a user-space address (addr < TASK_SIZE). This is because the lock of tsk->mm only protects the virtual memory of user address space, furthermore, dumping the page tables of a kernel-space address for user faults is unnecessary and may have security implications. Keep everything unchanged for kernel faults, because the kernel is already in the "oops" state, acquiring a lock may risk a deadlock. Co-developed-by: Qi Xi Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults") Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com Acked-by: Lorenzo Stoakes (ARM) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- rust/helpers/task.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 rust/helpers/task.c (limited to 'rust/helpers/task.c') diff --git a/rust/helpers/task.c b/rust/helpers/task.c new file mode 100644 index 000000000..c0e1a06ed --- /dev/null +++ b/rust/helpers/task.c @@ -0,0 +1,62 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include + +__rust_helper void rust_helper_might_resched(void) +{ + might_resched(); +} + +__rust_helper struct task_struct *rust_helper_get_current(void) +{ + return current; +} + +__rust_helper void rust_helper_get_task_struct(struct task_struct *t) +{ + get_task_struct(t); +} + +__rust_helper void rust_helper_put_task_struct(struct task_struct *t) +{ + put_task_struct(t); +} + +__rust_helper kuid_t rust_helper_task_uid(struct task_struct *task) +{ + return task_uid(task); +} + +__rust_helper kuid_t rust_helper_task_euid(struct task_struct *task) +{ + return task_euid(task); +} + +#ifndef CONFIG_USER_NS +__rust_helper uid_t rust_helper_from_kuid(struct user_namespace *to, kuid_t uid) +{ + return from_kuid(to, uid); +} +#endif /* CONFIG_USER_NS */ + +__rust_helper bool rust_helper_uid_eq(kuid_t left, kuid_t right) +{ + return uid_eq(left, right); +} + +__rust_helper kuid_t rust_helper_current_euid(void) +{ + return current_euid(); +} + +__rust_helper struct user_namespace *rust_helper_current_user_ns(void) +{ + return current_user_ns(); +} + +__rust_helper pid_t rust_helper_task_tgid_nr_ns(struct task_struct *tsk, + struct pid_namespace *ns) +{ + return task_tgid_nr_ns(tsk, ns); +} -- cgit v1.3.1